


Even Gods don't know

by TrueDespair_Yuuikida



Category: BNA: Brand New Animal (Anime), 文豪ストレイドッグス | Bungou Stray Dogs
Genre: Crossover, Gen, Major Spoilers, set after the anime series of BNA
Language: English
Status: Completed
Published: 2020-05-09
Updated: 2020-05-09
Packaged: 2021-03-03 01:09:08
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,092
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24086395
Author URL: https://archiveofourown.org/users/TrueDespair_Yuuikida/pseuds/TrueDespair_Yuuikida
Summary: After the events that occurred in Anima city, Shirou stumbled upon someone who was clinging for dear life and rescued them.Unknowing of the can of worms he just opened.
Relationships: Kagemori Michiru & Ogami Shirou, Nakajima Atsushi & Ogami Shirou
Comments: 6
Kudos: 77





	Even Gods don't know

**Author's Note:**

> Hello! It's been a hot minute. As you can already tell, I watched Brand New Animal and loved it. This is a first attempt of a crossover with the series so I hope you enjoy! I might write more crossovers in the future, who knows.

There were many things in the world that couldn’t be explained. Shirou knew this by heart, after living for so long and protecting all the beastmen that he could. He was old and hurt and, in many ways, so very tired. Sometimes he would hear the voices of the ones that had been killed in Nirvasyl all those years ago and while they mean no harm to him, it couldn’t erase the fact that he was an immortal being, forever standing still in an ever-changing world.

Even so, to think that he would find himself stumbling upon a body that was clinging to dear life on a broken piece of wood just outside of Anima City harbor was still not as surprising but nonetheless shocking.

Before he knew it, he jumped into the water and fished the body out, noticing that it was young man, no older than eighteen and soaked to the bone. When he got them onto the pier, he was relieved to know that the young man was still breathing but very pale. What surprised him though was the scent that he picked up from the young man. It was a scent that confused him and rarely did that occur. Either way, he shouldn’t judge so harshly at that moment as he was trying to change and understand humans with some fragile hope of humans understanding beastmen.

With that in mind, he shifted into his wolf form and hurried to the nearest hospital for the young man can be tended to, just as the sun was rising.

\--

The first thing he noticed was that he was on a soft bed, that was a foreign feeling. He slowly opened his eyes and realized that he really wasn’t laying on the floor but in a room. He can faintly hear people come and going not too far from him. He groaned as he blinked, his vision clearing. “….Where am I?”

“You’re awake. That didn’t take long at all.” 

Moonlight eyes slowly looked towards the right and that was when he realized that he wasn’t alone in the room.

Sitting on a chair and situated on the side of the bed was a man who didn’t look that much older than himself, maybe about a decade at most. White hair, light eyes and wearing something like vaguely seem like detective outfit thanks to the coat but with another blink, he noticed that the man had a scar on his neck and it looked like a very old one.

“Well?” The man spoke up again. “Are you alright or do you need a minute?”

Gulping, he blinked a few times. “S-Sorry…”

“There is nothing to apologize for.” The man stated. “I’m getting ahead of myself.” He rubbed the back of his head. “Do you know where you are right now?” When he got a shake of ‘no’ from the other, he sighed as he crossed his arms. “You’re at a hospital in a place called Anima City. I found you in the waters at the harbor, you were lucky that you were spotted when I came around.” He leaned back on the chair.

“….Oh…is that what happened….” The young man murmured before he sighed in resignation, but it was mixed with confusion. He then looked to the man and bowed his head. “Thank you for saving me….um…”

“Shirou Oogami.” The man replied. “Let’s just say I’m a social worker for the city. And you are…?”

For a moment, the young man was looking around as if searching for the answer before he blinked and smiled. “I’m Atsushi. Atsushi Nakajima, it’s nice to meet you Oogami-san!” He smiled a bit sheepishly. “Sorry, I don’t really remember much before I woke up here. I only remember is my name and…” His smile faded as he gripped the sheets. “Um….”

Studying the other’s expressions and movements, Shirou knew that now wasn’t the time to press. “It’s nice to meet you too, Atsushi.” He stood up from the chair. “In any case, the only thing you need to worry about is getting better. If you still can’t remember anything important then I’ll see to it that you’ll be situated in a good temporary home and have you registered as a citizen in the city.” Maybe he wasn’t doing things that was strictly social work, but he was still a social worker among other things. “I would stay long but I got work to do. So here is my card, I’ll come by to see you and pick you up when you’re discharged hopefully tomorrow.”

Taking the card, Atsushi looked it over and smiled. “Thank you so much.” He felt as though this was the most anyone has ever done for him in a long time but that felt like a lie somehow. He then noticed that it was sunset and he sighed. He hoped he can get a good night’s rest later on. “I don’t know how I can repay you—”

“Don’t worry about that.” Shirou raised his hand. “Just worry about getting better. Have a good night.” He nodded his head as he turned to leave. He opened the door and closed it behind him.

Though Atsushi picked up the sounds of someone else (a girl?) just outside of his room, he didn’t get much else as he relaxed and went back to laying down. “…I wonder…what happened to me…why can’t I remember anything?”

\--

“An anomaly?”

“Yeah.” Shirou was looking out of the windows of the town center building, his eyes on nothing in particular. “I picked up the scent of that young man and noticed two things. He has the scent of a human but at the same time, I picked up a scent of a beast,” He closed his eyes. “The scent made me assume that the beast is lurking behind him. It’s nothing I have ever seen and we had Michiru and Nazuna come into the city not too long ago.”

The mayor glanced at Shirou and hummed in thought. “Well, for someone to be an anomaly is a rare case indeed. We can’t rule that if he was experimented on or came into some beastman blood like those young ladies by accident. And what happened to that purebred Alan—”

Shirou growled a bit. He still detested that so called _beastman_.

“In any case, I’ll make some calls to see if there is a missing person case open. Hopefully with the name, we can find his family or at least his residence before too long. Can I trust you to watch over him in the meantime?” The mayor asked.

Soon a very faint smile came onto Shirou’s lips as he nodded. “Of course.” He looked up and noticed the full moon that was shining so brightly in the night sky—

A sudden rumble of an explosion was heard as the town center vibrated just a bit, causing those inside to be on guard.

“What was that?” The mayor was up on her feet and looking at the window with Shirou. “Don’t tell me we have a new wave of terrorists.”

Just then Shirou’s cell phone started to ring. He picked up the call quickly. “Michiru, what’s happening?”

“ _Shirou! It’s the hospital! I was walking back home with Nazuna and we heard a boom and went to check it out. We didn’t see anything but something white going into the city. We’re trying to find it but it was too fast for us to see it!”_

Sighing, Shirou nodded. “Got it, I’ll be in the city soon, don’t do anything stupid, alright?” He hung up before getting a response. He shifted into his wolf form and closed his eyes. He lifted his head up a bit as he searched for any peculiar scent. He quickly picked up the scent of various beastmen either going on their own business in one area or running for their lives in another. Soon he was able to pick up that scent, the scent that he just got acquainted with. A human scent and the beast lurking within, he got the location soon enough. “Mayor, I’ll handle the situation, please follow through with notifying the powers that be!” He was out of the room in record time, the mayor unable to say anything in return.

\--

“Wah…I don’t think I have ever seen someone like that before.” Michiru murmured as she and Nazuna were hiding behind the corner of a building. “They don’t seem to be doing anything other than just running around and sniffing things.”

Sighing, Nazuna crossed her arms. “Is it another experiment or something gone wild? I wouldn’t be surprised if someone were to try it.” She still had some resentment from that cult she was in and that Alan guy.

“I don’t know…but we better move or else---” Michiru pulled Nazuna out of the way with a yelp as whatever it was ran themselves against the very corner they were hiding in. They fell over as a result as she groaned. “Ow…that hurt…!” She gasped as she and Nazuna were face to face with—

“Michiru! Watch out!” Just then a light colored wolfman came out nowhere and planted himself between the girls and what was before him. “Are you two alright?”

Nodded, the girls smiled. “We’re fine,” Michiru started. “But more importantly, what are we going to do with that….beast?”

Looking forward, Shirou couldn’t believe his eyes. Before him was…a white tiger. Tigers weren’t as common in Anima City but to see a white tiger was very rare and to be in full beast mode, he dreaded to wonder. “It can’t be….!” The last time any beastman would be in full beast mode and causing chaos, could it be that the Nirvasyl syndrome was still lingering somehow? “That scent…that Atsushi guy….it doesn’t make sense…!”

“Who? That new guy you mentioned?” Michiru questioned. “He didn’t seem to be someone to could be a beast!”

“Maybe there is more to him than we can figure out.” Shirou turned to the girls. “I’ll handle him, contact the police and help them with damage control.”

Michiru didn’t really like playing backstage to any fight but she knew that Shirou wouldn’t let her just sit on her hands and wait. “Fine, but please be careful.” Taking Nazuna’s hand, they ran as far as they can before they took flight.

Shirou smiled as the girls took flight but turned his attention to the white tiger before him. “I don’t know how you got into full beast form or why you decide to wreak havoc on the city but I love this city and I won’t let anyone have it fall into ruin!”

The white tiger narrowed their moonlight eyes before they roared, so loudly that Shirou winced before they charged before him.

He didn’t live a thousand years for nothing. Shirou was faster and more experienced in battle than possibly anyone in the world but something about fighting an actual tiger was new to him. The tiger was nothing but resilient and quick on their feet as well. He tried to lead the tiger to a place where there wasn’t a lot of people and he had to be a bait to do so.

Soon they were at the very harbor where Shirou picked up the young man from the waters. With that in mind, Shirou started charging at the tiger and managed a kick at it but they bounced out and started going after him. It was a fight against mere animals with claws and teeth. The more they fought, the more that Shirou realized that the tiger was taking little to damage whereas he had to regenerate to heal his wounds. He was backing off to get another hit when the tiger went and gave him a huge, nasty bite to his arm.

Shirou yelled in pain before he growled and gave a hard kick to the tiger which made the tiger let go of him but also left him a bloody mess. He held his arm as he frowned. “Apart from the rampaging beasts before, this is a tough one. I guess I’ll have to knock it out.” Taking a few deep breaths, he ran towards the tiger with a yell and before the tiger thought to move, he briefly transform into his Ginrou form and proceeded to slam the tiger into one of the warehouses.

There was a beam of glowing bright blue light coming through the opening on the roof before it went out just as it came.

The inside of the warehouse though was wreck with a huge crater in the middle. Out of the rubble was Shirou who was coughing and cracking his neck. “That should put you down long enough until the authorities get here….” He trailed off as the smoke cleared and saw not a tiger but the young man once again.

Atsushi looked a bit bruised but compared to Shirou, he got off very lightly in terms of injury. He appeared to be sleeping almost soundly like he was used to sleeping on the ground.

Staring at the young man before shaking his head, Shirou went to pick up the young man, wanting to just get out of the warehouse. “You are one weird one indeed, and I know Michiru.”

\--

“I’m very sorry.” Atsushi bowed his head. He was standing in front of the mayor, Shirou and couple other people as they were situated in the main office of the town center. “I…what happened to me has happened before…my memory is still coming back to me but I swear I don’t recall what happened when I went to sleep last night. If there is any punishment for my actions regardless, I’ll face them had on.”

Michiru looked a bit uncomfortable. She can tell that it wasn’t his fault, not intentionally but still, some the buildings in the city were damaged. “Hey now, what’s done is done and we know you didn’t mean to—”

“You take responsibility for the actions taken whether or not you knew about it.” Shirou cut in but then relented as he sighed. “But considering your situation, I’m sure no punishments will be dealt with for unknowingly rampaging. It’s not the first we’ve seen it so you are not to blame for, personal speaking anyway.” He let out a faint smile even as Michiru gave his arm a weak punch.

“I agree.” The mayor stated. “Compared to what we have been through this is a minor thing and only the hospital suffered damage. Do not worry, it has been resolved and the hospital should be up and running before the week’s end.”

Atsushi nodded but still felt bad. “Thank you for your kindness.” He bowed his head again.

“Now, now, let’s let bygones be bygones.” The mayor smiled. “It’s a good thing though this is brought to our attention.” She stood up with her cane. “Speaking of, I took the liberty to put your name in the missing person database to see if any family members came up but none came up.”

“Not even residence of some sort?” Shirou asked.

“Not a thing.” The mayor replied. “It is as if he never existed before you found him.”

Michiru thought for a moment. “Maybe it’s because he’s been taken at a young age and only had his name because he was old enough to remember it.” She supposed. “He might be the few that didn’t get the serum from outside the city.”

“That would explain the full beast mode and his rampaging. High levels of stress triggered the beast genes and all….” Though Shirou had his doubts as the tiger he fought wasn’t mutated or in a blind rage like the others.

The mayor hummed. “Well it would be a good idea to give him a check up to see if that’s the case. An anomaly as Atsushi Nakajima is as a rarity as Michiru or even Shirou—”

“Um…excuse me….” Atsushi raised his hand. “What are you guys talking about? I hope I don’t offend you all, but I don’t really need a checkup. I had this ability for as long as I can remember which isn’t long since I can recall having it hidden from me for most of my childhood.”

The room was soon filled with silence.

“Wait, um, ability?” Michiru asked. “But you just changed into a tiger.”

“Yeah but that’s my ability, though sometimes not by choice. I was told that I would go into the other form when the moon is full and just…wander around.” Atsushi explained. “I mean you change into a form from your ability, right?”

Everyone stared at Michiru who was looking at herself with arms moving about. “A-Ability? No I just stuck like this because of the beast blood in me, I thought that’s why happened to you!”

Atsushi was surprised. “You mean you don’t have an ability to change forms?” Beast blood, what? “Like what I saw while coming there with you guys.”

“How can one have an ability to change into a beast form from a human so easily, either you’re a beastman or not!” Shirou stated.

Yelping a bit, Atsushi shook his head. “I’m telling the truth, apart from that I’m as human as human can be.” He looked at them. “Also, what is a beastman?”

Everyone was stunned. It was if they were just whacking back and forth in the conversation with no one winning. One thing they can agree on was that this was very confusing for all of them.

“It seems we’re at an impasse.” The Mayor spoke up. “No doubt that the young man was telling the truth but it raises more questions then answers. We should get to the bottom of this, until then, he is going to be under the protection of none other than Ginrou himself while we solve this mystery.”

“Ginrou?” Atsushi looked at the man or was a man but now in wolf humanoid form. He was startled as he took a step back. “Whoa…how is that even possible?”

Shirou though known as Ginrou in beastman mythology, sighed as he placed a hand on his head. “I would like to say the same thing to you.” He though he had seen it all, in all of his years of living in this world.

Unknown to him, this was just the beginning, for him, for the group and for the city. A beastman that _isn’t_ a beastman?

What was the world coming to?

\--

**END**

**Author's Note:**

> Unless I continue this, I'll leave it up to the readers on how Atsushi ended up in Anima City of all places~


End file.
